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Original post by Acrux
Un=k+(100-1)k
=100k


Not quite. You've correctly identified that a, the first term, = k, and the difference is k in the series, so Un = k + (n-1)k.

You don't know what n is, but you know that Un, the final term (since there are n terms) is .... so ...
Reply 21
Original post by Math12345
Careful.

Count the bits in the brackets (1,2.....)


Brackets is from 1- 100 which is 100 terms
Original post by Acrux
Brackets is from 1- 100 which is 100 terms


No it's from 1 to 100/k.

So how many terms?
Reply 23
Original post by SeanFM
Not quite. You've correctly identified that a, the first term, = k, and the difference is k in the series, so Un = k + (n-1)k.

You don't know what n is, but you know that Un, the final term (since there are n terms) is .... so ...


so 100=k+(n-1)k
100=kn
n=100/k

so you cant assume there are 100 terms as it goes from k to 100?
Original post by Acrux
so 100=k+(n-1)k
100=kn
n=100/k

so you cant assume there are 100 terms as it goes from k to 100?


Correct.

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